Render final image in pieces (EEVEE)
Actually you should be able to render 4k without slicing the image into parts, however here some options:

&quot;Slicing&quot; you can create several view layers and always render a part of the image and combine then later in your editing software of choice
&quot;Splitting&quot; you can split your scene in foreground, background etc and combine the layers in compositing blender guru 2.7 sample
&quot;Add-on&quot; there is also an add-on (not sure if it's for 2.8+) set render border addon

This question also got asked at stack exchange previously